Voice control

If you need more detailed control over how samples are played, you can use
the lower level voice functions rather than just calling play_sample(). This
is rather more work, because you have to explicitly allocate and free the
voices rather than them being automatically released when they finish
playing, but allows far more precise specification of exactly how you want
everything to sound. You may also want to modify a couple of fields from the
SAMPLE structure. Read chapter "Structures and types defined by Allegro" for
its definition.